Updating maps for GPS, Viable?

[oldbmw]

It was my intention to update the maps for my satnav every other spring, but the original up to date maps (2011) will direct me to a supermarket that was demolished in 1998 and which has been a college since 1999. It also does not know of the hypermarket that replaced the original supermarket (also in 1999) and which is about half a mile from the original site. A few times I have been on roads which have obviously been there a few years ( trees well grown at the side) which it thinks are fields or open country. It misspells the name of my farm and local hamlet so you can't input the name to navigate to it and Today it tried to direct me across some fields where a road used to be many years ago, some traces can still be seen under the trees which I guess to be 15-20 years old.

Given the cost of the upgrade and the need to spend 19 hours online for a down load ( the server usually disconnects you after about 12 hours) I have come to the conclusion it might just be better to buy a new "up to date"? unit every few years..

What are other peoples experiences?